JP2897442B2 - Optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive suitable for use in, for example, an optical or magneto-optical disk reproducing apparatus, a recording apparatus, a recording and reproducing apparatus, and the like.

[0002]

2. Description of the Related Art A conventional optical disc reproducing apparatus is shown in FIG.
This will be described with reference to FIG. In FIG. 11, an optical head 30 detects information recorded on an optical disk (not shown). An arithmetic circuit 31 is an optical head 30
, And outputs an information reproduction signal and a focus error signal having an S-shaped characteristic. 60 is an adder,
The focus error signal from the arithmetic circuit 31 and the voltage from the volume 61 are added. Also, this volume 61
One end is connected to the positive power supply + B, and the other end is connected to the negative power supply -B.

An addition output signal (control voltage signal) from the adder 60 is supplied to a phase compensation circuit 36 and a buffer amplifier 3.
7, and is supplied to a focus actuator 38 described later. The focus actuator 38 moves the objective lens of the optical head 30 in the optical axis direction according to the voltage value of the control voltage signal from the buffer amplifier 37. As a result, the laser beam emitted from the optical head 30 is focused on the optical disk.

The above-mentioned optical head 30, arithmetic circuit 3
1 and the focus actuator 38 form an optical system circuit as shown in the figure, and the adder 60, the volume 61, the phase compensation circuit 36 and the buffer amplifier 37 form a signal processing system as shown in the figure. These optical systems and signal processing systems are usually mounted on separate printed circuit boards.

In the above-mentioned optical disc reproducing apparatus, manual adjustment is indispensable. For this adjustment, the optical disk is reproduced by the optical head 30, the oscilloscope probe is brought into contact with the output side of the arithmetic circuit 31, and the amplitude of the waveform of the information reproduction signal is visually observed on the oscilloscope screen. That is, the volume 61 is made variable so as to be the maximum.

[0006]

The above-described FIG.
1B has the following disadvantages.

First, manual adjustment must be performed. Since the optical system and the signal processing system are mounted on different printed circuit boards, for example, when one of them is replaced, the adjustment must be manually performed again.

Further, a bias voltage for obtaining an optimum focusing state changes due to a change with time, that is, a change in alignment of an optical component of an optical pickup or a change in environment, for example, a rise in temperature. Unless the volume value (resistance value) of the adjusted volume is adjusted again, the accuracy of the focus servo becomes low.

In view of the above, the present invention eliminates the need for adjustment when replacing one of the optical system circuit and the signal processing system circuit, and also eliminates changes in the alignment of the optical components of the optical pickup with time, environmental changes such as temperature changes, and the like. Nevertheless, an object of the present invention is to propose an optical disk drive device capable of performing highly accurate automatic focus adjustment.

[0010]

According to the present invention, there is provided an optical disk drive in which tracking optical recording traces Tp are alternately formed at predetermined intervals on both sides of a track along a track. Focus error detecting means 3 for detecting a focus error signal indicating a deviation of the focused beam Li from a focused state on the optical disk.
1 and calculating means 31, 32, 33 for calculating the average value of the peak value of the reproduction signal waveform of the optical recording trace Tp for tracking on both sides of the track by the optical head. The bias that maximizes the absolute value of the average value from the operation means 31, 32, and 33 is added to the error signal, and the added output gives
An actuator 38 for moving the objective lens of the optical head 30 in the optical axis direction is controlled.

[0011]

According to the present invention, the focus error signal from the focus error detection means 31 is added to the arithmetic means 3
1, 32, and 33, the absolute value of the average value is added to the bias, and the added output provides the optical head 30.
The actuator which moves the objective lens in the optical axis direction is controlled.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIG. 1. In the case of using a magneto-optical disk capable of erasing recorded data among optical disks. explain. FIG. 1 shows an optical disk recording / reproducing apparatus (recording apparatus or reproducing apparatus) according to the present invention. An optical head 30 detects information recorded on an optical disk (not shown). An arithmetic circuit 31 calculates a detection signal from the optical head 30 and outputs an information reproduction signal and a focus error signal having an S-shaped characteristic.

Reference numeral 32 denotes a signal processing circuit which extracts a wobble pit reproduced signal, which will be described later, from the reproduced signal from the arithmetic circuit 31, and calculates this. The operation output signal from the signal processing circuit 32 is supplied to the CPU 33 through a bus (comprising data, address, and control bus) Bu.
CPU33 is based on focusing information signal to be described later based on the calculated output signal from the signal processing circuit 32 supplies a bias, i.e., the offset to the operational amplifier 35 through the D / A converter 34 and a resistor R _1. The arithmetic circuit 3
The focus error signal of S-characteristic from 1 is a resistor R ₂
To the operational amplifier 35. The CPU 33
Is supplied with a detection output from a temperature sensor TS provided in the recording / reproducing apparatus and rotation information of the disk. The disk rotation information may be either a detection output from a frequency generator (FG) provided in the spindle motor or information obtained from a disk reproduction signal.

The input and output sides of the operational amplifier 35 are:
It is connected by a negative feedback resistor R _3. An output signal (control voltage signal) from the operational amplifier 35 passes through a phase compensation circuit 36 and a buffer amplifier 37, and a focus actuator 38 for driving an objective lens (not shown).
Supplied to

Therefore, the objective lens of the optical head 30 is moved in the optical axis direction by the focus actuator 38 so that the laser beam emitted from the optical head 30 is focused on the optical disk.

Next, a sample format type magneto-optical disk will be described with reference to FIG. FIG. 7 shows a part of the recording area of the magneto-optical disk. The recording area of the magneto-optical disk is divided into a plurality of sectors, each sector is provided with a sector mark, and based on a gray code used for identification with an adjacent track and for access at the same time. Identification pit G formed
A clock pit Cp for obtaining p and data sampling timing is provided on the virtual center line of the track. The data to be recorded or the recorded data is arranged on the virtual center line of the track on the downstream side in the moving direction (arrow a) of the light beam spot Li. In order to record data along the virtual center line of this track or to reproduce the recorded data, it is necessary to apply tracking servo to the light beam, but in order to obtain a tracking error signal for applying tracking servo, A pair of wobble pits Tp offset from each other by １ ／ of the track pitch with respect to the virtual center line of the track are provided at positions offset from each other. Therefore, when the light beam spot Li moves on the virtual center line of the track, the two peak values of the detection output when passing through the pair of wobble pits Tp are equal to each other, but the light beam spot Li is virtual. When moving at a position deviated from the center line (for example, a position above or below the virtual center line of the track in FIG. 7), 2 of the detection output when passing through a pair of wobble pits Tp is obtained. Since one of the two peak values is larger than the other, a tracking error signal can be obtained by calculating the difference between the two peak values. Next, the optical head 30 described with reference to FIG. 1 will be described in detail with reference to FIG. here,
An orthogonal coordinate system including an x-axis and a y-axis forming an xy plane on the paper surface and a z-axis perpendicular to the paper surface and extending upward is set in advance.

In FIG. 2, reference numeral 1 denotes a semiconductor laser element (laser diode). After a laser beam directed in the + y-axis direction is supplied to a collimator lens 2 and formed into a parallel beam, each of the laser beams has a right-angle cross section. The light is incident on a semi-transparent mirror surface of a beam splitter 13 which is integrated with an isosceles triangular glass prism 13A and is formed by laminating a pair of glass prisms each having a right-angled isosceles triangular cross section. The s-linearly polarized beam reflected by the semi-transparent mirror surface and directed in the −x-axis direction is emitted from the beam splitter 13.

A portion 4 surrounded by a broken line indicates an optical system and a head portion located in a direction perpendicular to the paper surface, and is drawn on the paper surface, that is, in the xy plane for convenience of drawing. The s-linearly polarized beam reflected by the semi-transparent mirror surface of the beam splitter 13 and traveling in the −x-axis direction is reflected by the reflecting surface of the glass prism 5 whose cross section of the optical system 4 is a right triangle,
After being deflected in the + z-axis direction, it is converged by the objective lens 6 to form the perpendicular magnetic film 7 of the magneto-optical disk 7.
a and is reflected there. The reflected beam has its polarization plane slightly rotated with respect to the incident beam in accordance with the state of magnetization of the magnetization film, and a predetermined ellipticity is generated to be an elliptically polarized beam.

The divergent beam directed in the −z-axis direction reflected by the magnetic film 7 a of the disk 7 is converted into a parallel beam by the objective lens 6 and then reflected by the reflecting surface of the prism 5.
After the optical path is deflected in the + x-axis direction, it is incident on the beam splitter 13 and is reflected by the semi-transparent mirror surface, whereby the optical path is deflected in the + y-axis direction. By passing through a λ / 2 plate 9 having an optical axis on the inner surface in the direction of 22.5 degrees, a beam composed of an s-polarized component and a p-polarized component (when there is no signal, the amplitude of both components is After being converted into (equal), it is incident on the condenser lens 10 and focused. Then, the focused beam from the condenser lens 10 enters the photodetector 15. When data is recorded on the magneto-optical disk 7, the magnetic field generated by the external magnetic field generating means 4a provided on the optical axis of the objective lens 6 on the opposite side of the magneto-optical disk 7a is used. The recording laser beam is focused on the magneto-optical disk 7 via the optical disk and irradiated, thereby recording data on the magneto-optical disk 7.

Next, the configuration and operation of the photodetector 15 will be described with reference to FIGS. The photodetector 15 includes a polarization beam sprick 16 and a pair of photodetectors 17 and 18 formed on the same substrate.
9 are integrally formed. The polarizing beam splitter 16 includes a glass prism 16A having a cross section of a right-angled isosceles triangle and a parallelogram having a cross section of 45 ° and 1 °.
35 °) and a glass prism 16B.

The focused beam from the condenser lens 10 is incident on the incident surface 16a of the prism 16B at a right angle, and a dielectric multilayer film 16b is provided on a joining surface having an angle of 45 degrees with respect to the incident surface 16a. Have been. The dielectric multilayer film 16b allows the p-polarized component of the incident beam to pass and reflects the s-polarized component.

The dielectric multilayer film 16 of the prism 16B
The parallel surface 16c parallel to b is a reflection surface for the above-mentioned s-polarized light component. And the polarizing beam splitter 1
6, the s-polarized light component reflected and separated by the dielectric multilayer film 16b is reflected by the reflection surface 16c and emitted.
6B and the surface 16e of the dielectric multilayer prism 16A.
Are the same plane. Each of the exit surfaces 16d and 16e of the polarization beam splitter 16 is at a position shifted by the same distance back and forth with respect to the focal point P of the focused beam entering from the entrance surface 16a.

Next, the photodetector 19 will be described. This photodetector 19 is composed of a pair of photodetectors 17 and 18 formed on the same substrate.
B and 16A are in contact with the surfaces 16d and 16e. As shown in FIG. 4, the photodetectors 17 and 18 are each divided into three strips, and the optical axes of the s-polarized component and p-polarized component beams are positioned at the center positions of the central detectors 17B and 18E. I try to match.

Then, as shown in FIG.
When the spots SPs and SPp of the s-polarized light component and the p-polarized light component irradiated on the photodetectors 17 and 18 have the same diameter as shown by the solid line, the magnetic film of the disk 7 is irradiated. The optical path is adjusted in advance so that the focused beam is focused on the magnetic film. Thus, the focused beam irradiated on the magnetic film of the disk 7 is
When the convergence on the magnetic film 7a is deviated, the light detecting unit 17,
The diameter of the beam spot on the spot 18 changes reciprocally as shown by a broken line and a dashed line in FIG.
The detection output corresponding to the change in the diameter of SPs is output to the light detection unit 1 respectively.
7,18.

Next, each light detecting section 1 of the light detector 19
Regarding the operation circuit of the light detection output obtained from 7, 18
This will be described with reference to FIG. Each light detector 1 of the light detector 17
The detected outputs from 7A, 17B, and 17C are A, B, and C, respectively.
And each of the light detection units 18D, 18E, 18 of the light detection unit 18
The detection outputs from F are D, E, and F, respectively.

In FIG. 4, reference numerals 21 to 24 denote adders, and reference numerals 25 to 28 denote operational amplifiers. Then, the detection outputs A and C are added by the adder 21, and the operational amplifier 25
Then, the addition output A + C of the adder 21 is subtracted from the detection output B, and the operation output FE ₁ = B− (A + C) is obtained. The detection outputs D and F are added by the adder 23 and the operational amplifier 27
Then, the addition output D + F of the adder 23 is subtracted from the detection output E, and the operation output FE ₂ = E− (D + F) is obtained. In the adder 22, the addition output A + C of the adder 21 and the detection output B
Are added, and the adder 24 outputs the addition output D + of the adder 23.
F and the detection output E are added, and the operational amplifier 26 calculates the addition output RF ₁ = A + B + C of the adder 22 from the adder 24.
Summed output RF ₂ = D + E + F of subtraction, arithmetic output RF = RF ₁ -RF ₂ is obtained, which becomes the reproduced information signal from the disk 7. An operational amplifier 28, calculated from the calculated output FE ₁ from the amplifier 25, is computed output FE ₂ of the operational amplifier 27 is subtracted, calculated output FE = FE ₁ -FE
₂ is obtained, and this becomes the focus error signal.

Next, the signal processing circuit 32 described with reference to FIG. 1 will be described with reference to FIG. 51 converted by A / D converter, a reproduction signal from the input terminal T ₁ into a digital signal, which registers 49c, 49
a, 49d, 49e, 49b, and 49f, respectively, and to a sync pattern detection circuit 53 through a binarization circuit 52.

The sync pattern detection circuit 53 detects a sync pattern for each segment (= 18 bytes),
A load control signal is supplied to a segment counter 54 described later. When a sync pattern is first detected from the time of initialization, the switch SW is turned on to close the PLL loop, and thereafter, this state is maintained.

The segment counter 54 receives a clock signal (for example, 12.3M) from a voltage controlled oscillator 59 described later.
Hz), and when the load control signal is supplied from the sync pattern detection circuit 53, the counter is initialized.
The count value of the segment counter 54 is supplied to the decoder 55. Then, from the decoder 55, each register 49
Control signals are supplied to clock signal input terminals of c, 49a, 49d, 49e, 49b, and 49f, respectively. This is because there is information of a reproduced signal to be detected when a certain number of clock signals are counted from the sync pattern and to be held in each register.

As a result, each register 49c, 49
For a, 49d, 49e, 49b and 49f, the mirror level Dm of each sample point c, a, d, e, b, f of the waveform of the reproduced signal of the tracking pit Tp as shown in FIG. Data Dc, Da, Dd, De,
Db and Df are supplied and held. Here, a and b indicate the peak points of the waveforms of the reproduction signals of a pair of pits constituting the tracking pit Tp, and c, d; e, f.
Are the points on both sides of the peak points a and b, respectively, and the times between the points ca, ad, eb, and bf are equal to each other.

Numeral 46 denotes a (Da + Db) / 2 arithmetic unit, which is data Da of the sample point a from the register 49a, and
Data Db of sample point b from register 49b
And an operation of multiplying by １ ／ is performed. Then, the signal of the operation result is transferred to the bus B described with reference to FIG.
is supplied to the CPU 33 through u. This signal is on-track, without being so much depends on the state of said off-track, of whether the light beam is in focus on how correctly on disk for a maximum value when connecting properly focused on the optical disk It can be used as focusing information. Also,
The disc has uneven reflection and wobble pit formation during one rotation.
33 is an appropriate number of times per rotation, for example, 30 times (Da
+ Db) / 2 The configuration is such that data is obtained from the arithmetic unit 46, and further, data of a total of 60 samples is obtained per two rotations of the disk, and averaging processing is performed. Focus information.

Numeral 47 denotes a (Da-Db) arithmetic unit, which is obtained from the data of the sample point a from the register 49a.
Performs an operation of subtracting the sample point b of the data from the register 49b, through the D / A converter 48, to the output terminal T ₃ the result as an analog signal (tracking error signal).

The reproduced signal of the wobble pit Tp, as shown in FIG. 7, the reproduction by the light beam Li is irradiated to a pair of pits formed alternately to the left and right of the virtual center line T ₀ of the track However, if the pair of pits is uniformly irradiated with the light beam Li, as shown in FIG. 6B, the amplitudes Da and Db of the reproduced signals of both pits are equal with respect to the mirror level Dm. Become. However, when the two pits are not uniformly irradiated with the light beam Li, the amplitudes of the reproduced signals of the two pits are different from each other as shown in FIGS. Therefore, at this time, (Da
-Db) The arithmetic unit 47 outputs a tracking error signal.

Reference numeral 56 denotes a phase error calculation circuit,
The subtraction result (Dc-Dd) obtained by subtracting the data Dd of the sample point d from the register 49d from the data Dc of the sample point C from c, and the sample point f from the data De of the sample point e from the register 49e to the sample point f from the register 49f. Is added to a subtraction result (De−Df) obtained by subtracting the data Df of (Dc).
-Dd) + (De-Df)] is multiplied by 1/2. Then, the result [(Dc-Dd) + (De-D
f)] / 2 is supplied to a voltage controlled oscillator 59 through a D / A converter 57, a phase compensation circuit 58 and a switch SW.
Is supplied as an oscillation frequency control signal. The clock signal from the voltage controlled oscillator 59 is output to the output terminal T ₄ , A /
It is supplied to the clock signal input terminals of the D converter 51 and the segment counter 54, respectively.

Next, referring to the flowchart of FIG.
The automatic offset adjustment operation of the focus servo according to the present invention will be described, and its effectiveness against environmental changes such as temperature, changes over time, and replacement of the optical head will be described.

First, in step ST-1, a switch (power switch) is turned on. Then, the process proceeds to the next step ST-2.

In step ST-2, the rotation of the spindle starts, that is, the rotation of the spindle starts the rotation of the magneto-optical disk. And the next step ST
Shift to -3.

In step ST-3, the rotation of the spindle is stabilized. Then, control goes to the next step ST-4.

In step ST-4, a laser beam is emitted from the semiconductor laser element (laser diode) 1 of the optical head 30 (laser ON). Then, control goes to the next step ST-5.

In step ST-5, the output of the D / A converter 34, that is, the focus bias is forcibly set to O.
Set to V. Then, the process proceeds to the next step ST-6.

In step ST-6, the sweep of the focus actuator 38 is started. Then, the process proceeds to the next step ST-7.

In step ST-7, the focus pull-in ends. Then, control goes to the next step ST-8.

In step ST-8, the offset of the automatic focus is adjusted. The details of the operation in step ST-8 will be described later with reference to FIG. At this time, although the tracking servo performs the focus offset adjustment in the off state, the tracking servo is turned on and off because the offset amount is adjusted using the value of (Da + Db) / 2 as described later. There is no particular problem since there is almost no difference in the OFF state. Conversely, offset adjustment can be performed while the tracking servo is ON. Then, control goes to the next step ST-9.

In step ST-9, a drive standby state is set. Then, the process proceeds to the next step ST-10.

[0045] In the step ST-10, carried out the measurement of the temperature, to store the temperature T _1. The temperature detection signal from the temperature sensor 60 is converted into a digital signal by an A / D converter (not shown) and supplied to the CPU 33 through the bus Bu shown in FIG. Then, control goes to the next step ST-11.

In step ST-11, the presence or absence of an off command is determined. If YES, the process proceeds to step ST-12, and if NO, the process proceeds to step ST-14.

In step ST-12, a process for terminating the operation of the driving device, that is, an off process is performed, and then in step ST-13, the reproducing device is brought into an operation end state, ie, an off state.

In step ST-14, temperature measurement is performed. The measured temperature is defined as T _2, and thereafter, step S
The process moves to T-15.

In step ST-15, | T ₁ -T ₂ |
It is determined whether the temperature is> 5 ° C., and if NO, step S
The process proceeds to T-11, and if YES, the process proceeds to step ST-15.
Move to At 5 ° C. where | T ₁ −T ₂ |> 5 ° C., the set value may be changed as necessary.

At step ST-16, at step ST-
The same automatic focus offset adjustment as in step 8 is performed, and then the process proceeds to step ST-10.

Next, the automatic focus offset adjustment by the CPU (see FIG. 1) 33 in steps ST-8 and ST-16 in FIG. 8 will be described with reference to the flowcharts in FIGS. First, in FIG. 9, in step ST-1, the output of the D / A converter 34, that is, the focus bias value is set to OV. That is, FIG.
The bias data signal supplied to the D / A converter 34 shown in (1) is changed to a data signal corresponding to OV. Then, control goes to the next step ST-2.

In step ST-2, focusing information is collected,
That is, (Da + Db) output from the signal processing circuit 32.
/ 2 value by adding for example 60 times based on the rotational information of the disk is supplied to the CPU 33, to obtain an average value A ₁ by dividing the addition result by 60. Then, step ST-3
Move to. In this case, the addition 60 times is performed on the magneto-optical disk 1.
It was detected 30 times during rotation (every 12 ° in angle) (D
a + Db) / 2 means to collect two rotations. By doing so, it is possible to eliminate the influence of the noise of the RF signal, the reflection unevenness during one rotation of the disk, and the influence due to the uneven formation of the wobble pit.

In step ST-3, the output of the D / A converter 34, that is, the focus bias value is set to B (unit voltage is positive). That is, the D / A converter 3
4 is a signal corresponding to + B (V). As a result, the in-focus state can be offset by an amount corresponding to + B (V). Then, control goes to the next step ST-4.

In step ST-4, step ST-2
In the same manner as in (1), focusing information is collected, that is, the signal of the result of (Da + Db) / 2 from the signal processing circuit 32 is added, for example, 60 times, and the addition result is divided by 60 to calculate an average value.
Here its the calculated average value A _2. Then, control goes to the next step ST-5.

In step ST-5, step ST-4
Subtraction result the average value A ₁ was calculated by subtracting from the average value A ₂ was calculated in step ST-2 in (A ₂ -A
_{When 1} = C) is smaller than 0, the next step ST-6
To step ST-1 in FIG.
Move to 4.

In step ST-6, step ST-4
Instead of the average value A ₂ of the calculated focusing information (Da + Db) / 2 of the result of the signal in, using the average value A ₁ in step ST-2 calculated focus information (Da + Db) / 2 results . Further, the focus bias value is set to 0. That is, the bias data signal supplied to the D / A converter 34 is changed to a data signal corresponding to OV. As a result, the focus state returns to the original position (the position where the focus bias is zero). And the next step ST-
Move to 7.

In step ST-7, the currently set focus bias value is set to a value obtained by subtracting B from the current focus bias value. And the next step ST-8
Move to.

In step ST-8, step ST-7
It is determined whether or not the focus bias value set in step S is smaller than the limit value -L.
The process moves to T-9, and if NO, moves to step ST-10.

In step ST-9, it is determined that an error has occurred in the automatic focusing due to the offset. In this case, the fact may be reported to a host computer connected to the optical disk drive via an interface such as SCSI.

In step ST-10, step ST-
The bias value of the focus set in 7 is supplied to the D / A converter 34 as a bias data signal. Then, similarly to steps ST-2 and ST-4, the average value of the focus information (Da + Db) / 2 signal (this average value is represented by A ₃
Is calculated). Then, control goes to the next step ST-11.

In step ST-11, step ST-
Calculated focus information 10 (Da + Db) / 2 of calculated previously set from the average value A ₃ of the result of the signal-focus information (Da
+ Db) / 2 of the average value A ₂ of the resulting signal by subtracting, the subtraction result (a D) is shifted to the next step ST-12 If 0 or more, is smaller than 0 step ST
Move to -13.

[0062] In step ST-12, the calculation, instead of the average value A ₂ of the focusing information (Da + Db) / 2 results in signal set previously, focusing information calculated in step ST-10 (Da + Db) / 2 using the average value a ₃ of the result of the signal, the process proceeds to step ST-7 again repeats the same operation as described above.

In step ST-13, it is determined that the optimum bias value for automatic focus is a value obtained by adding B to the current value, and this value is set as the bias value for focus. That is, the optimum bias value (D / A converter 34
Is an integral multiple of -B (V). And it ends.

Next, referring to FIG. 10, in step ST-14, the currently set focus bias value is set to a value obtained by adding B to the current focus bias value. Then, control goes to the next step ST-15.

In step ST-15, step ST-
The focus bias value set in 14 is the limit value +
It is determined whether or not L is larger than L. If YES, the process proceeds to step ST-16, and if NO, step ST-1.
Move to 7.

In step ST-16, it is determined that an error due to offset has occurred in the automatic focus. still,
In this case, the fact may be reported to the host computer connected to the disk drive device through an interface such as SCSI.

In step ST-17, step ST-
The focus bias value set at 14 is supplied to the D / A converter 34 as a bias data signal.
Then, similarly to steps ST-2 and ST-4, the average value of the focus information (Da + Db) / 2 signals (this average value is represented by A
₃ ) is calculated. And the next step ST-18
Move to.

In step ST-18, step ST-
Focus information calculated by 17 (Da + Db) / 2 of calculated previously set from the average value A ₃ of the result of the signal-focus information (Da
+ Db) / 2 of the average value A ₂ of the resulting signal is subtracted, the next step S when the subtraction result (a D) is greater than 0
The process proceeds to T-19, and if smaller than 0, the process proceeds to step ST-.
Move to 20.

[0069] In step ST-19, the calculation, instead of the average value A ₂ of the focusing information (Da + Db) / 2 results in signal set previously, focusing information calculated in step ST-17 (Da + Db) / with 2 results in the signal mean value a ₃ of, the process proceeds again to step ST-14, the above-described operation is repeated.

In step ST-20, it is determined that the optimum automatic focus bias value is a value obtained by subtracting the current value B, and that value is set as the focus bias value. That is, the optimum bias value (voltage of the D / A converter 34) is an integral multiple of + B (V). And it ends.

Thus, every time the focus is turned on,
Further, every time the temperature changes by 5 ° C., an automatic offset adjustment operation of the focus servo is performed, so that it is possible to cope with various situations such as environmental changes such as temperature, changes over time, replacement of the optical head, etc., and always keeps the optimum focus state. be able to.

In the above-described embodiment, the offset adjustment of the automatic focus is performed in a state where the tracking is not performed. However, the same adjustment can be performed in a state where the tracking is performed. In the embodiment, the reproducing apparatus using the magneto-optical disk has been described. However, the present invention is not limited to the magneto-optical disk, but can be used for other optical disk reproducing apparatuses.

[0073]

According to the present invention described above, in a drive apparatus for an optical disk in which tracking optical recording traces are alternately formed at predetermined intervals on both sides along a track, a focused beam from an optical head is provided. Error detecting means for detecting a focus error signal indicating a deviation from the in-focus state on the optical disc, and an average value of peak values of a reproduction signal waveform of an optical head for tracking optical recording traces on both sides of the track. Calculation means for calculating the focus error signal from the focus error detection means, a bias that maximizes the absolute value of the average value from the calculation means is added, and the added output allows the objective lens of the optical head to be added. Since the actuator that moves in the optical axis direction is controlled, one of the optical system circuit and the signal processing system circuit is controlled. Along with the adjustment is unnecessary at the time of exchange,
High-precision automatic focus adjustment can be performed irrespective of changes over time such as alignment of the optical pickup and environmental changes such as temperature.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of an optical head.

FIG. 3 is a diagram illustrating an example of a photodetector.

FIG. 4 is a diagram illustrating an example of a light detection unit and an arithmetic circuit.

FIG. 5 is a diagram illustrating an example of a signal processing circuit.

FIG. 6 is a waveform diagram of a reproduction signal of a tracking pit.

FIG. 7 is a diagram showing a sample format of an optical disc.

FIG. 8 is a flowchart.

FIG. 9 is a flowchart (1).

FIG. 10 is a flowchart (No. 2).

FIG. 11 is a diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 30 optical head 31 arithmetic circuit 32 signal processing circuit 33 CPU 38 actuator Tp tracking pit Li light beam

Claims (1)

(57) [Claims] 1. An optical disk drive in which tracking optical recording traces are alternately formed at predetermined intervals on both sides along a track, wherein a focused beam from an optical head is formed on the optical disk. A focus error detection means for detecting a focus error signal indicating a deviation from the in-focus state; and a calculation for calculating an average value of peak values of a reproduction signal waveform of the optical recording trace for tracking on both sides of the track by the optical head. Means, and a bias that maximizes the absolute value of the average value from the calculating means is added to the focus error signal from the focus error detecting means, and the objective lens of the optical head is moved by the added output. An optical disk drive, wherein an actuator that moves in the optical axis direction is controlled. .